迭代器能减少内存空间实现循环。
方法1：
1 import time 2 from collections import Iterable 3 from collections import Iterator 4 5 6 class Classmate(object): 7 8 9 def __init__(self): 10 self.names = list() 11 12 13 def add(self,name): 14 self.names.append(name) 15 16 17 def __iter__(self): 18 """如果想要一个对象变成一个可以迭代的对象，即可以使用for,那么必须实现__iter__方法""" 19 return Classmator(self); # 调用Classmator 然后把自己传过去 20 21 22 class Classmator(object): 23 def __init__(self,obj): 24 self.obj = obj 25 # 定义索引值 26 self.current_num = 0 27 28 def __iter__(self): 29 pass 30 31 32 def __next__(self): 33 # 判断索引值是否超出列表个数范围 34 if self.current_num < len(self.obj.names): 35 ret = self.obj.names[self.current_num] 36 # 索引值+1 37 self.current_num += 1 38 return ret 39 else: 40 # 抛出异常，终止for循环 41 raise StopIteration 42 43 classmate = Classmate() 44 45 classmate.add("张三") 46 classmate.add("张二") 47 classmate.add("李四") 48 49 # 判断一个类型是否可以迭代 isinstance(要判断的对象，Iterable) 50 print("判断classmate是否是可以迭代的对象：", isinstance(classmate,Iterable)) 51 # 迭代器 52 classmate_iterator = iter(classmate) 53 # 判断classmate_iterator是否是迭代器 54 print("判断classmate_iterator是否是迭代器：", isinstance(classmate_iterator,Iterator)) 55 # print(next(classmate_iterator)) 56 57 for name in classmate: 58 print(name) 59 time.sleep(1)
两个类可以改善成一个，只要有__iter__方法和__next__方法：
1 import time 2 from collections import Iterable 3 from collections import Iterator 4 5 6 7 class Classmate(object): 8 def __init__(self): 9 self.names = list() 10 self.current_num = 0 11 12 def add(self,name): 13 self.names.append(name) 14 15 16 def __iter__(self): 17 return self 18 19 20 def __next__(self): 21 if self.current_num < len(self.names): 22 ret = self.names[self.current_num] 23 self.current_num += 1 24 return ret 25 else: 26 raise StopIteration 27 28 29 classmate = Classmate() 30 classmate.add("张三") 31 classmate.add("李四") 32 classmate.add("王五") 33 34 # 判断一个类型是否可以迭代 isinstance(要判断的对象，Iterable) 35 print("判断classmate是否是可以迭代的对象：", isinstance(classmate,Iterable)) 36 # 迭代器 37 classmate_iterator = iter(classmate) 38 # 判断classmate_iterator是否是迭代器 39 print("判断classmate_iterator是否是迭代器：", isinstance(classmate_iterator,Iterator)) 40 # print(next(classmate_iterator)) 41 42 for name in classmate: 43 print(name) 44 time.sleep(1)
